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SubjectRe: [Patch 1/6] dm: endio method
Mike,

On Sat, Feb 21, 2004 at 01:58:38AM -0800, Mike Christie wrote:
> Saving and restoring bi_bdev is going to break multipath.

Yes, we'll have to fall back to plan A and use the map_context pointer
to hold the path being used (attached patch for illustration only). I
had been hoping we could keep the map_context unused so that we could
allow the path selectors to use it. I should have spotted this.

I'll also move the failed bio remap back to mpath_end_io(), so that
the context can be reused there (it moved to the daemon when we were
trying to do path testing in the kernel).

- Joe


--- diff/drivers/md/dm-mpath.c 2004-02-18 15:51:06.000000000 +0000
+++ source/drivers/md/dm-mpath.c 2004-02-23 09:58:31.000000000 +0000
@@ -219,7 +219,7 @@ static struct path *get_current_path(str
return path;
}

-static int map_io(struct multipath *m, struct bio *bio)
+static int map_io(struct multipath *m, struct bio *bio, union map_info *map_context)
{
struct path *path;

@@ -228,6 +228,7 @@ static int map_io(struct multipath *m, s
return -EIO;

bio->bi_bdev = path->dev->bdev;
+ map_context->ptr = path;
return 0;
}

@@ -517,29 +518,13 @@ static int multipath_map(struct dm_targe
struct multipath *m = (struct multipath *) ti->private;

bio->bi_rw |= (1 << BIO_RW_FAILFAST);
- r = map_io(m, bio);
+ r = map_io(m, bio, map_context);
if (r)
return r;

return 1;
}

-/*
- * Only called on the error path.
- */
-static struct path *find_path(struct multipath *m, struct block_device *bdev)
-{
- struct path *p;
- struct priority_group *pg;
-
- list_for_each_entry (pg, &m->priority_groups, list)
- list_for_each_entry (p, &pg->paths, list)
- if (p->dev->bdev == bdev)
- return p;
-
- return NULL;
-}
-
static void fail_path(struct path *path)
{
unsigned long flags;
@@ -570,8 +555,8 @@ static void fail_path(struct path *path)
static int multipath_end_io(struct dm_target *ti, struct bio *bio,
int error, union map_info *map_context)
{
- struct path *path;
struct multipath *m = (struct multipath *) ti->private;
+ struct path *path = (struct path *) map_context->ptr;

if (error) {
spin_lock(&m->lock);
@@ -581,7 +566,6 @@ static int multipath_end_io(struct dm_ta
}
spin_unlock(&m->lock);

- path = find_path(m, bio->bi_bdev);
fail_path(path);

/* queue for the daemon to resubmit */
-
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